1. Field of the Invention
The present application relates to an over-current protection device, and more particularly to an over-current protection device with low resistance and superior trip jump behavior.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Because the resistance of conductive composite materials having a positive temperature coefficient (PTC) characteristic is very sensitive to temperature variation, it can be used as the material for current sensing devices, and has been widely applied to over-current protection devices or circuit devices. The resistance of the PTC conductive composite material remains extremely low at normal temperature, so that the circuit or cell can operate normally. However, when an over-current or an over-temperature event occurs in the circuit or cell, the resistance instantaneously increases to a high resistance state (e.g. at least 102Ω), so as to suppress over-current and protect the cell or the circuit device.
Generally, PTC conductive composite material includes one or more crystalline polymers and a conductive filler. The conductive filler is evenly dispersed in the polymer. The polymer may be polyolefines such as polyethylene, and the conductive filler may be carbon black. However, the carbon black has low conductivity, so that it cannot meet low resistance requirement.